The long-time parental absence has shaped Fang. It has taught him to believe that order and disorder in his life were not due to fate or the actions of others, but self-determination.

"He is no doubt more mature than his peers. He is quiet, cautious and patient. These qualities are often seen on other left-behind children," says Fang's teacher Wang Shihai. He notes that nearly 20 percent of almost 6,000 students in the school are left-behind children.

"I often hide from strangers and I seldom talk about my worries with others," Zhiqian says. "My brother is even more withdrawn, and he has more pressures on study. He is already getting grey hair."

Independent researcher Ruan Mei has closely observed the lives of the children. She has spent four years interviewing more than 3,000 left-behind children in the six major migrant worker-exporting provinces of Sichuan, Shaanxi, Hunan, Hubei, Anhui and Henan. She just wrote a book entitled Pains Of The Century: Investigation Into China's Left-behind Children.

"The reality is astonishingly painful. What concerns me is how ignorant we are of the pains of the children. They grow upon their own," says the former reporter of the Huarong Newpaper based in Huarong County of Hunan Province.

The 44-year-old woman says two suicide cases of left-behind children inspired her to look into the issue four years ago. "One boy committed suicide for not studying well and another girl drowned herself for being pregnant. Many such cases, including rape and murder, also appeared in my investigation."

"But the most serious problem that the children face concerns their psychology. More than 40 percent of my child interviewees are obviously impaired," she says.

More than 16 percent of the children thought that their parents didn't love them and more than 80 percent said they felt insecure.

The left-behind children are usually of low self-esteem, oversensitive, and don't get along with others. Many hide their emotions and pretend to be happy.

"Their pains are like the moon during the day; invisible but it's still present," she says.

The "left-behind children" issue has aroused the attention of the Chinese government. A special work team, led by the State Council, was set up to establish a long-term strategy to protect the legitimate rights and interests of left-behind children through laws and regulations.

In addition, some local governments have provided left-behind children allowance for their living and medical care, while the Ministry of Education has built and renovated more than 10,000 boarding schools in central and western China to ensure the children receive an appropriate education.

However, Ruan insisted that family and school, the main caregivers for the children, are the key to tackle the problem.

"The educational level of adults supervising these children is generally not that high. Often they can only care for the children's safety and daily living, but their educational, behavioral and spiritual needs," says Ruan.

She suggests that family education should be added in the vocational training programs for migrant workers to teach how to communicate and educate the children. Psychology courses and psychological teachers should be introduced in schools.

"Regular letters from their parents and chats with teachers are the best remedy," says Ruan.

Xie Kui'e went back to Luoshan in the last June to take care of the sons till they finish the college entrance examinations. She rents a flat in downtown and sends meals to the two boys everyday.

Although she is still worrying about the expense of their college education, she hopes the rare reunion would help their studies.

Her return is a great encouragement for Zhiqian, who said his happiest moments now were when he has lunch with his brother and mother.

"Now I have people to talk to about my troubles and worries. I feel supported," he says.

In the future, Xie Kui'e and Zhiqian have different pictures: Xie hopes she can support her two sons while they finish their college education. Then she will renovate their house. Zhiqian dreams of studying economics at university and going back with that knowledge to develop his hometown after graduation.

"Then, nobody will need to leave home to earn money and there will be no left-behind children anymore," he says.